When to use the LPF Setting TOS9300 Series

Posted on: June 23rd, 2021 by Doug Lovell

The TOS9300 series of electrical safety testers is a robust all-in-one solution. When performing AC Hipot, DC Hipot and Insulation Resistance tests there are setting options which allow the user to optimise testing as necessary for all applications. In certain situations where EUT’s are being tested for very high insulation resistances the LPF can be used to significantly improve the accuracy of the tester.

The LPF of the TOS9300 series is a second order Bessel filter with a 3dB cutoff at 1 kHz. This filter was designed to remove the transmission line noise that causes stray capacitance to affect the measurement. Any application that expects an insulation resistance measurement higher than 50 M ohm should consider using the LPF.
When measuring high insulation resistances at high voltages we expect to see very low currents measured at the ammeter because of Ohm’s Law. Readings where the expected current is only nA are greatly affected by high frequency noise. This type of noise is hard to avoid so it is useful to have a LPF which removes the high frequency current components just before measurement. It should be noted that a longer test time should be used to compensate for the lower frequency signal being measured in the test. See the operation manual for more information.

Products Mentioned In This Article:

  • TOS9300 Series please see HERE